John Langer Consulting

Therefore the coordination of MEP systems must satisfy multiple objectives and criteria for design, installation, commissioning, operation, and maintenance. Different types of specialty contractors (e-g., process piping, HVAC piping, WAC ductwork, plumbing, electrical, fire protection, controls) are responsible for these systems. Examples of diverse criteria for system design include spatial (avoiding interferences), functional within a system (flow or gravity drainage), adjacency or segregation, system installation (layout dimensions, space and access for installation productivity), and testing (ability to isolate). On complex buildings and plants, expertise and designs are required from diverse specialists – essential fragmentation requiring horizontal integration between these different functions working in the same project phase.

The current work process is for design consultants or design-build contractors to design their systems independently. Coordination responsibility is then assigned to one firm, often the general contractor, the HVAC contractor, or a coordination consultant. The resulting process is slow and expensive. One general contractor estimated coordination costs as six percent of the MEP cost or two percent of the total cost on a light industrial project. An electrical contractor said that coordination cost equals design cost on projects in Silicon Valley; each are about three percent of the total cost for electrical systems.

Although not used as often, at the low-tech end of the practice spectrum for MEP coordination, drawing plan views on transparent media and using a light table to overlay routing contractors is easy to understand and change. However, this process often involves frequent and difficult meetings. Difficulty in visualizing complex systems in congested spaces often requires drawing multiple section views to accompany the plans prepared for initial routing. It is also very difficult to accommodate design change after coordination decisions.

At the other end of the spectrum, 3D CAD and other information technology (BIM) offers the potential to improve this process and its results. Plant models provide major benefits for large hydrocarbon and power projects on which the Architect / Engineer completes the entire design.

However, design consultants and specialty contractors prefer systems tailored to specific information needs for detailing, estimating, fabricating, and tracking their type of work. Current use of multiple systems tailored to the needs of specific disciplines and trades limit overall effectiveness. Some systems are not compatible and DXF transfer usually loses about ten percent of the database contents.

Complex configurations of MEP systems in congested spaces are very difficult to visualize.

The less complete definition of systems in the “design assist” approach makes it very difficult to define scope of work for fixed price contracts. This increases the potential need for contract changes based on the increased cost of installing the system configuration that results from the coordination process. Also, the first contractor working in an area often optimizes routing for their systems; requiring expensive rework if this is not compatible with other systems.

As a result of these problems with current processes, the product of MEP coordination does not fully satisfy the objectives of any of the project participants. To improve project performance, the construction segments focused on complex buildings and high tech plants need increased horizontal integration between design consultants or design-build contractors to improve the effectiveness of the coordination process and better meet project objectives.

Complex buildings and light industrial projects, using the design-bid-build approach, the design assist approach or the design-build approach, require coordination for MEP systems. The engineer first prepares mechanical, plumbing and electrical specifications, assigning full responsibility for coordination to the specialty contractors, including checking for clearances, field conditions, and architectural conditions. On design-bid-build projects, the engineer also prepares diagrammatic drawings of MEP systems to establish the scope, materials, and quality, but not detailed layout or installation instructions. The specification requirements and drawings provide the information inputs for MEP coordination.

After contract award, the process for MEP coordination begins with the specialty contractors (primarily HVAC wet and dry, plumbing, electrical, and fire protection) preparing shop drawings to route systems, details for fabrication, and locate for installation. Representatives from each of the specialty contractors then sequentially compare their shop drawings using a light table. They also prepare section views for highly congested areas, identify interferences, decide which contractor will revise their design, and submit requests for information regarding problems that require engineering resolution. This sequential comparison overlay process follows a consistent priority described below and continues until all interferences are resolved. The product of this process is a set of coordinated shop drawings that are submitted to the engineer for approval. The specialty contractor may also submit the cost impacts of coordination, which can be significant if the coordinated system differs greatly from typical configurations.

The current process for MEP coordination presents the following problems on many projects: The scope of services by the engineer does not include coordination; detailing information defining configuration is required and only available from the specialty contractor. Responsibility for engineering, design, detailing, and as-builting is difficult to define, the scope of coordination and the responsibility for each trade are not clearly defined. The coordination process is slow; it can become critical path for systems installation.

The current approach requires extensive commitment of key staff having very valuable experience by the engineer, general contractor, and specialty contractor. Constructible design depends on the construction knowledge of contractor’s detailer. Operable systems depend on the operations knowledge of contractor’s detailer. The process creates potential for commercial disputes concerning scope and complexity; allowance for scope growth during coordination can increase the cost of MEP systems and the construction schedule of projects.

Design of MEP systems under design-bid-build contracts

In the traditional design-bid-build scenario, the architect has control of the building envelope. The architect designs the structure to meet the needs of the owner. These needs are usually in the form of the space and shape of the structure as well as the aesthetic aspects of the building.

In the design-bid-build project delivery method, the architect employs an engineering design consultant to work under them for the purpose of designing the MEP systems.

It is the engineering design consultant’s responsibility to design each system in the building. These systems include HVAC dry, HVAC wet, plumbing (gravity driven systems), plumbing (pressure driven systems), electrical, and telecommunications, security, and data. In more high-tech facilities, this list would also include process piping. In designing the various systems, the engineering design consultant performs a detailed analysis and prepares design calculations for each of the systems. Sizing of each system component is made. This information is conveyed to the specialty contractors in the form what is referred to as contract drawings or design drawings. They are referred by their particular trade or discipline, i.e., mechanical design drawings, electrical design drawings, plumbing design drawings, etc. (The level of detail provided to the specialty contractor will be described in a following section.)

Currently, the MEP coordination process begins when all building systems have been designed and preliminarily routed. The design is finished when all components are sized (e.g., conduits, pipe, HVAC duct), the engineering calculations completed, and the schematic drawings produced. This means that specific routing is not defined. Usually the HVAC and piping systems are sized during this initial design. Other trades such as electrical and fire protection is not, therefore some of the systems are drawn to scale while others are drawn simply as lines with references to component sizes.

The coordination process begins with the all the specialty contractors meeting together with all of their particular designs and preliminary drawings.

The routing of the various building systems follows the necessary path that each system must take to reach its desired location. Most of this routing is determined by the design from the architect and structural engineer. Common constraints that determine routing locations are the building structure, corridors, shear walls, fire walls, major equipment locations, and architectural requirements, such as ceiling type and interstitial space. The preliminary routing drawings reflect these constraints; each trade routes their system to their own advantage. This includes minimizing the length of branches and number of fittings, choosing prime locations for major components, routing close to support points, and designing for most efficient installation by their own trade.

The proposed methodology of MEP coordination would place the MEP coordinator early in the design phase, preferably at the late programming, early design phase. This should be accomplished by having the Owner hire an independent third party to administer the process from the design thru construction and startup and after the project is completed to verify the operations and adequacy of the systems. Figures 1 – 5 below outline the proposed process for design-bid-build (plans and specifications project). Much of the flow chart can be used for a design-build project and even with GCCM or GCCM at Risk.

Figure 1 shows the recommended point where MEP coordination should be interjected into the design process. It is the function of the MEP Coordinator to support and advise the design team during the design and not to act as the designer.

Figure 1.

Figure 2 shows the continued collaboration between the MEP coordinator and the design team. In a design-build project, the MEP coordinator would be closely working with the design team, general contractor and the subcontractors thru design development and into construction documents. In a design-bid-build project, the earlier the MEP coordinator is brought on board, the fewer conflicts and associated change orders during construction.

Figure 2.

Figure 3 shows the added responsibilities of the MEP Coordinator in assuring that the MEP project impacts or potential impacts are addressed and resolve by the time the project is in the bidding process. During the bidding phase, the MEP coordinator is used as a tool in responding to clarifications and addenda that may be issued.

Figure 3.

Figure 4 shows the areas where the MEP Coordinator adds value to the project team and ultimately the finished product.

Figure 4.

Figure 5 shows the value and timing of the use of MEP coordination to get the maximum value for the project during the pre-construction phase.

Figure 5.

In recent years, the author has provided MEP coordination on projects, both as a member of the Contractor’s team and as the Owner’s Representative. Between 1993 and 1994 provided MEP coordination for the “ZymoGenetics South Lake Union Steam Plant” facility while with Lease Crutcher Lewis, a Seattle, WA based general contractor. This project included the renovation of a historic structure along South Lake Union, restoring it to its original grandeur, while at the same time providing a state-of-the-art research facility. On this project, MEP coordination was incorporated early in the design phase. The design elements were analyzed, submitted on electronic media by the architects, structural engineer and design-build subcontractors, using CAD to physically overlay the drawings, giving a bird’s-eye view of traffic problems.

Once conflicts were identified, solutions were developed by the MEP coordinator and the team and information was distributed to designers for incorporation into the documents. Each team member was encouraged to provide input. As the design progressed, the analysis process continued, with constant checks for new conflicts.

The team ran into many potential traffic problems that could have been disastrous in the long run. For example; the main feeds to the electrical rooms had to be rerouted from the tie-in point to Seattle City Light. That meant changing the location of fire protection riser room and plumbing systems to provide clearance.

Using 3D CAD, the existing third floor roof trusses were overlaid on the HVAC design drawings then duct routing was developed and the duct itself was fabricated and installed. Most of theduct in the truss spaces was about 50 inches in diameter and would barely fit through the spaces. Yet, due to the design efficiencies, incorporating MEP coordination only one piece of duct had to be re-fabricated out of over 50,000 pounds of duct installed. In addition, it was estimated that between $15,000 and $20,000 was saved because there was no wasted efforts in the field locating pieces of duct and waiting for fabrication.

Another benefit of the MEP coordination and use of 3D CAD, was identifying added useable spaces. While reviewing the interior wall plans, and thru MEP coordination, tweaking the design of certain mechanical shafts would create added useable space without affecting the mechanical requirements. The plans of all other related work disciplines were overlaid to confirm no other conflicts existed, and with the Owner’s approval, design drawings were revised.

The benefits of MEP coordination, and its associated costs, is beneficial to any client by savings of money and time and the reduction of conflicts above the ceiling tiles.